Warm the milk and lemon zest in a small saucepan until steaming. Remove from the heat and add 25g butter, swirling until it has melted and the milk has cooled slightly.
Mix 500g flour, 1 tsp cinnamon, the caster sugar, yeast and 1 tsp salt in a large bowl. Pour in the milk mixture and one of the beaten eggs, then combine with a wooden spoon until the mixture clumps together. Tip out onto your work surface and knead until smooth and elastic, about 10 mins – the dough should bounce back when pressed with your finger. Transfer to an oiled bowl, cover with a tea towel and leave to rise for 2 hrs or until doubled in size.
While the dough rises, make your cinnamon butter. Mash the remaining butter and cinnamon with the light brown sugar.
Dust your largest baking tray with flour. Tip the dough onto the work surface and knead again to knock out any air bubbles. Roll the dough to a rectangle roughly 30 x 40cm. Spread the cinnamon butter over the dough, covering the whole surface. Scatter over the dried fruit. From one of the longer edges, roll up the dough into a tight sausage shape. Use a sharp knife to cut the dough into 12 equal-sized pieces. Arrange them on the tray, leaving a small gap between each one and making sure the open end of the scroll is facing inwards to prevent them springing open as they cook. Cover loosely and leave somewhere warm to prove for 1 hr or until almost doubled in size – the buns should be just touching.
Heat oven to 180C/160C fan/gas 4. Brush the buns with a little beaten egg. Mix the remaining 140g flour with enough water to make a thick, smooth paste, then transfer to a piping bag fitted with a small round nozzle (or use a sandwich bag with a corner snipped off ). Use the paste to pipe crosses over the buns, then bake for 25 mins until deep golden brown and cooked through.
Leave to cool for 10 mins on the tray. Meanwhile, mix the cream cheese and icing sugar, then brush the mixture over the warm buns. If you have any excess, you can serve this on the side for spreading over. Eat the buns warm from the oven or leave to cool. Will keep for up to two days in an airtight container.